1. Chapter 8 Percentage Composition

2. Water is made of hydrogen and oxygen. How many grams of each are in the sample of water below?

3. Percent Composition Mass of element Formula Mass of compound X 100 X 100 % = Percent composition is the percent by mass of an element within a compound. Divide the mass of each element by the formula mass of the compound

4. Percent Composition of H 2 O 2 X H = 2 X 1.0 g = 2.0 g 1 X O = 1 X 16.0 g = 16.0 g gram formula mass = 2.0 g + 16.0 g = 18.0 g % H = 2.0g X 100 = 11.2% 18.0g % O = 16.0g X 100 = 88.8% 18.0g

5. Percent Composition of H 2 O 2 X H = 2 X 1.0 g = 2.0 g 1 X O = 1 X 16.0 g = 16.0 g gram formula mass = 2.0 g + 16.0 g = 18.0 g % H = 2.0g X 100 = 11.2% 18.0g % O = 16.0g X 100 = 88.8% 18.0g What does this mean?

6. Pure water’s mass is 11.2% hydrogen and 88.8% oxygen. (0.112)(128.98g) = 14.45g H (.888)(128.98g) = 114.53g O or 128.98g – 14.45g = 114.53g O 11.2% H 88.8% O

7. Percentage Composition Remember that you have to calculate the formula mass!

8. Determine the Percent Composition of C 6 H 12 O 6

9. 6 X C = 6 X 12.0 g = 72.0g 12 X H = 12 X 1.0g = 12.0g 6 X O = 6 X 16.0g = 96.0g gfm = 180.0 grams/mole

10. Determine the Percent Composition of C 6 H 12 O 6 6 X C = 6 X 12.0 g = 72.0g 12 X H = 12 X 1.0g = 12.0g 6 X O = 6 X 16.0g = 96.0g gfm = 180.0 grams/mole % C = % H = % O = (72.0g/180.0g) X 100 = 40.0% (12.0g/180.0g) X 100 = 6.67% (96.0g/180.0g) X 100 = 53.3%

11. How many grams of carbon are in 156g C 6 H 12 O 6 6 (156g)(0.400) = 62.4g carbon 12 6 Molar % C = % H = % O = (72.0g/180.0g) X 100 = 40.0% (12.0g/180.0g) X 100 = 6.67% (96.0g/180.0g) X 100 = 53.3%

12. What is this? a

13. Iron Pyrite “Fool’s Gold” (FeS 2 ) a

14. How many grams of sulfur are in this 28.8g sample of iron pyrite FeS 2 ? a

15. a 15.4g S

16. How many grams of sulfur are in this 28.8g sample of iron pyrite FeS 2 ? a 15.4g S Fe + 2(S) 55.8 + 2( 32.1) = 120.0 g/mol %S = 64.2/120.0 x 100= 53.5%S 28.8g x 0.535 = 15.4g S

17. Homework  Molarity Worksheet (Due Tomorrow).  Percentage Composition Worksheet (Due in 2 Days).